WELD HEAT-AFFECTED ZONE IN TI-6AL-4V ALLOY .1. COMPUTER-SIMULATION OF THE EFFECT OF WELD VARIABLES ON THE THERMAL CYCLES IN THE HAZ

The weld thermal cycles encountered in the HAZ of titanium alloys have been characterized using modified Rosenthal equations. The results are shown in the form of axonometric plots depicting the effect of two weld variables keeping the other variables fixed. Computer simulation results show that the heat input and the plate thickness are the major variables affecting the thermal cycles in the HAZ. The effects of changes in welding speed are reflected in the variation in the heat input. The electrode radius has minimal effect and can be termed as the minor variable. Preheat or interpass temperatures have an intermediate effect. An increase in electrode radius or decrease in plate thickness requires large apparent displacement of the heat source above the plate surface to be incorporated in the analytical solutions. The melt pool width increases sharply with an increase in the heal input (q/v) or a decrease in plate thickness (d); however, preheat temperature (T-o) has negligible effect. The effect of weld variables on the effective hear input is also similar. The t(8/5) parameter increases sharply with reducing plate thickness or increasing heat input.